Upgrade to Rails 3.2 and use Bootstrap

This is quite a big branch, but it should make Need-o-tron a lot easier to use now.

- Upgrade app to Rails 3.2.13. 
- Added [Bootstrap](http://twitter.github.io/bootstrap) to the layout and all the views. 
- Substantial layout change to the individual need page, tidying it up.
- Replaced the javascript behind the nested attribute fields (for policy owners and fact checkers) with [nested_form](https://github.com/ryanb/nested_form) helpers.